External Beam Radiation Therapy (EBRT) is used in the disease management of more than half of all cancer patients worldwide. Recent advances in EBRT delivery regimens (e.g., Stereotactic Body Radiation Therapy) and tumor detection methods (e.g., molecular imaging) pave the way for the treatment of increasingly small lesions with increasingly high ablative radiation doses to maximize local control rates. In light of these trends, high dose conformality is important for delivering curative dose to the target while sparing surrounding healthy structures. Random and quasi-periodical anatomy motion during beam delivery poses a fundamental threat to realizing such conformality, and thus restricts the curative potential of EBRT.
Existing and emerging technologies for localizing abdominal targets during beam delivery employ tracking of implanted fiducial markers, tracking of external surrogates, or guidance via magnetic resonance images. However, these technologies cannot provide real-time, volumetric, non-invasive, markerless, soft-tissue image guidance capabilities with existing radiation delivery platforms. Thus, a significant opportunity exists to improve the widespread technical capability and clinical outcomes of EBRT.
Several key issues remain in the design of a system configured to image during radiotherapy, including: (1) reliably obtaining 3D ultrasound images over extended times with minimal interference to the radiotherapy workflow; (2) improving processing times for quantitative interpretation of ultrasound data; and (3) avoiding interference of the ultrasound transducer with radiation delivery. The system described herein is intended to solve some of these problems.